Soft magnetic materials are used in a variety of applications including magnetic heads, transformers, and magnetic shields. For example, U.S. Pat. No. 3,908,194 describes an integrated magnetoresistive read/inductive write head which includes soft magnetic permalloy shielding layers and a soft magnetic biasing layer in the MR stripe "sandwich". Desirable characteristics in such materials include low magneto-stiction, high saturation magnetization, high permeability, and low coercivity. The advantages associated with these characteristics should be familiar to those of ordinary skill in the art and will not be explained further.
A number of iron-based alloy films have been developed in recent years in an attempt to improve the foregoing characteristics. One approach has been to form amorphous thin films by conventional methods and to anneal them at a temperature of about 550.degree. C. in order to segregate a highly saturated .alpha.-Fe solid solution phase having a grain size of approximately 10 nm or less. The resulting alloys have high permeability, low magneto-stiction and saturation magnetization of 1.6-1.7 T. For example, Y. Yoshizawa and K. Yamauchi, disclose an alloy comprising Fe-Nb-Cu-Si-B in J. Japan Inst. Metals, Vol. 53 (1989) p. 241. K. Nakanishi et al. disclose an alloy having a composition of Fe-X-N, wherein (X=Zr, Hf, Nb or Ta) in J. Mag. Soc. Japan, Vol. 15 (1991) p. 371. N. Hasegawa et al. discusses an alloy comprising Fe-X-C where (X=Zr, Nb or Ta) in Bull. Japan Inst. Metals, Vol. 30(8) (1991) p. 685.
In another approach, a nano-scale crystalline Fe-M-O thin film (M=Y, Ce) is obtained through sputtering, as disclosed by A. Kojima and A. Makino in Japan Inst. Metals Spring Meeting Abstract, (1992) 4, p.187. The characteristics of the Fe-M-O thin films include saturation magnetization B.sub.s =1.95 T, coercivity H.sub.c =0.60 e, an initial permeability .mu.i (1 Mhz)=1200, and magneto-stiction .lambda.s=1.1.times.10.sup.-6.
An Fe-M-O film is also disclosed in PUPA No. 64-24403, wherein M represents at least one element selected from the group comprising (Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Os, Co, Ni, B, C, Al, Si, Ga, Ge, Sn, P, and Sb), the atomic percentage of which is less than 20 atomic percent. The oxygen composition of the film in atomic percentage ranges from 0.005 to 3%. The application further explains that the soft magnetic characteristics of the alloy can be improved by laminating films containing the described composition over heat resistant oxides like silicon oxide or holsterite. Immediately after sputtering, the laminated films have a saturation magnetization B.sub.s of approximately 2T, coercivity H.sub.c of 0.50 e, and an initial permeability .mu..sub.i (1 Mhz) of 1800. Such coercivity and permeability values, however, do not reach the technological level suited for high density magnetic recording.
Yet another approach attempted to improve the characteristics of iron-based alloys has been to prepare bulk material by a conventional alloy powder method. For example, PUPA No. 3-153851 discloses soft magnetic materials comprising Fe-M-X where (M=Co, Mo, Ti, Cu, Y, Ge, Gd, Sm, Nd, Dy, Si, and P); and X=N and H. However, the coercivity of such alloys is higher than that of the materials disclosed in PUPA No. 64-24403, making them unsuitable for high density magnetic recording.
What is needed is a soft magnetic material wherein the magneto-stiction, saturation magnetization, permeability and coercivity characteristics meet the technological requirements for high density magnetic recording.